When comparing Knockout vs Vue.js, the Slant community recommends Vue.js for most people. In the question“What are the best client-side JavaScript MV* frameworks?”Vue.js is ranked 1st while Knockout is ranked 2nd. The most important reason people chose Vue.js is:

Vue can easily be integrated with other front-end libraries. This makes it an extremely versatile tool and it's easy to fix its shortcomings or missing features by just plugging in another library.

Pros

Pro

Easy data binding

Knockout uses HTML5 data attributes to bind HTML elements to data objects in javascript. This allows more work to be done by the framework rather than requiring you to specify where data should be bound in the javascript. The data binding is very intuitive as the bindings are done within the HTML itself in the location it should be bound.

Pro

Easy to learn

Has a low entry barrier and an easy learning curve. It's especially easy to learn for beginners.

Pro

Built in templating

Bindings in Knockout can also be used to control the generated structure of the HTML. There are bindings provided to allow for iteration and conditionals. The structure of the html reflects the structure of the data so iterative elements are bound to arrays in the data model. Having the HTML structure maintained by bindings keeps the templating simple, easy to read, and maintain.

Knockout also allows for string based templating so you can use whatever templating library you prefer.

Pro

Dynamic models help with keeping the code simple and clean

Models in Knockout can be watched to keep the page data up to date by using observable objects. The observables notify Knockout when data is changed and automatically updates the page when this happens. By having Knockout maintain this relation, it keeps the front end code cleaner and simpler, and by enforcing a consistent pattern with observables the methodology can be more robust.

Pro

Legacy browser support

Supports a large number of browsers, including IE6.

Pro

Great documentation

The excellent tutorials with built-in exercises are a great learning experience, even for people without prior MVVM and data binding experience.

Pro

Very flexible

One can do a lot of things and it keeps self references and other types of loops under control.

Pro

Lightweight and plays nicely with other libraries

Pro

It's only a library

Knockout does one thing, and does it well. It doesn't try to take on more than one area. It does MVVM data binding and that is it.

Pro

Simple manageable modules

Using components is a great way of breaking up large modules into simpler ones.

Pro

Can be used with any front-end stack

Vue can easily be integrated with other front-end libraries. This makes it an extremely versatile tool and it's easy to fix its shortcomings or missing features by just plugging in another library.

Pro

Lightweight

Vue.js weighs in at 16kb min+gzip.

Pro

Single file component

Very useful.

Pro

Responsive server-side rendering

Since most of the mainstream server-side rendering implementations are synchronous, they can block the server's event loop when the application is complex.

Vue implements streaming server-side rendering, which allows you to render your component, get a readable stream and directly pipe that to the HTTP response. This allows you to have a responsive server and decreases the time your users have to wait before they get your rendered content.

Pro

Support for both templates and JSX

You can choose to use either a templating language, or if you feel it's necessary to drop on a lower virtual-dom level, you can use JSX. This is simply done by replacing the template option with a render function.

Or alternatively, you can embed functions inside templates by using the <render> tag.

Pro

Supports inline templating

Although you can build components in JavaScript files, you can also use inline handlebars-like templating in your HTML views where simplicity is often a more sane choice.

Pro

SEO friendly

Starting with Vue 2.0, Vue supports server-side rendering. This helps with SEO a lot, since the views are rendered directly on the server, which are indexed by search engines.

Pro

Can be made even lighter

Since the template-to-virtual-DOM and compiler can be separated, you can compile the templates in your machine and then deploying only the interpreter which is 12KB minified and gzipped.

Pro

Vuex store, events system

Pro

CLI and Webpack integration

Pro

Reactivity system

Pro

VueRouter

Cons

Con

Seems to be dead

KO has been stuck at version 3.4 for a long time, and there's not a lot of community activity.

Con

Can become complex once the application grows large

Knockout leaves the application structure to the developer and it can become quite complex and unmanageable in the hands of a beginner once the application grows large and complex.

Con

Two way binding requires a little extra work

When allowing users to edit existing data, the two-way binding of observables means you'll need to have to save original values before they're edited, to make comparisons or revert if the user cancels the action.

Con

Slower than others when amount of objects grows

Knockout has a bad performance when the dealing with large amount of objects. You can see more here.